London City Airport bomb find is just the tip of the iceberg

Following the discovery of an unexploded bomb in east London last weekend, TV treasure hunter Stephen Taylor tells us there is much, much more where that came from

Many people think that when a bomb hits the ground, it explodes. This is indeed the case in most instances, but the explosion has to be initiated by a fuze, and fuzes don't always work.

This means there is plenty of unexploded ordnance lying around the UK, dropped by the Germans during the Second World War. The most conservative estimate of the fuzes used by Hitler's airforce still puts failure rates at around 10%. In other words, at least one in every 10 bombs dropped didn't explode.

During the Second World War, just over 74,000 tons of bombs were dropped on UK soil (including the 'V' weapons) by the Luftwaffe, which means around 7,400 tons didn't explode. Many were recovered at the time and made safe, but large numbers either fell undetected, or buried themselves so deep they weren't worth trying to tackle. They were so deep as to be deemed 'not dangerous'.

But it isn't just German ordnance that litters the British countryside. The Allied armies needed somewhere to practice, so gunnery ranges were set up all across the country. If you consider the Home Guard also had gunnery ranges, the number of locations where the men practised with explosive ordnance numbers in the low thousands. Many of these sites went unrecorded, but all have the potential to hide unexploded ordnance like mortars and grenades.

For example, on soft ground, 2-inch mortars could have a failure rate of more than 20%. Even the well-known and easily recognised Mills bomb had failure rates in the mid to high single-figure range.

To try and put all this into perspective, here is just one of my own experiences of unexploded ordnance. During the filming of an episode of 'WW2 Treasure Hunters', in one field in a sleepy little village in Leicestershire, we recovered 88 rounds of live WW2 ammunition. Yep, 88 rounds. That is just one field, used as a camp and not even a gunnery range, in one little village.

The ordnance is scattered all across the UK. The German bombing campaign targeted cities, ports, towns with important factories and airfields, so unexploded aerial bombs tend to be concentrated around these sites. However, even the countryside can hide explosive surprises, with many areas of open farmland 'hit' by German bombs as they jettisoned their load in an effort to get home. For example, there is a book about wartime Leicestershire that shows known bomb hits, and also where known unexploded bombs lie buried. One stretch of the river Soar has around 10 unexploded German bombs buried in the flood plain.

This stack of live ammunition was found in a tiny patch of woodland while filming 'WW2 treasure hunters'. Calibres range from 9mm all the way up to big 50cal rounds. These were picked up by the police shortly after filming.

As for the ordnance on old army bases, airfields and gunnery ranges, the amount still buried out there amounts to thousands and thousands of tons, most of it only inches beneath the surface. When you think that every village, town and city had a Home Guard unit, it follows that there was a gunnery range where they could practice nearby. During the build up for D-Day, the Allied soldiers didn't just sit about and wait; they trained and trained and trained. They had to do it somewhere, and vast swathes of British farmland and coastal areas were converted to gunnery ranges.

Why hasn't this incendiary legacy of wartime been removed? Well the cost to locate and dispose safely of these items would be astronomical. You would have to search every square inch of land across the entire UK with magentometry, metal detectors and even ground-penetrating radar. Even then you would have to ensure you really did cover every square inch of land.

Some areas of known high concentrations of unexploded ordnance have been cleared in the past, by specialised military units, but we are talking dozens of sites. There are thousands more.

How much of the ordnance is active, you ask? Well this is difficult to say. One thing's for sure, just because an item of explosive ordnance has been buried for 70 years does not make it safe. I've lost track of the amount of times I have explained this to metal detectorists, who think that being buried for 70 years somehow neutralises explosives. It doesn't, and indeed in many instances the explosive compounds become more sensitive and far less predictable.

German bombs regularly carried anti-tamper fuzes, and many men lost their lives in WW2 trying to work out how to diffuse these lethal strips. They are likely to still be working today, so the modern disposal expert has the same challenge.The other issue you have with ground-based ordnance like mortar bombs is that the fuze arms as the weapon is fired. With 2-inch mortars, for example, the firing pin just needs the slightest of taps and it will set the whole thing off, and the top of that firing pin is on the very outside of the fuze.

Nerves of steel

Diffusing and disposing of unexploded ordnance is a highly skilled job and takes lengthy training and nerves of steel. All three branches of the UK armed forces has specialist explosive ordnance disposal (EOD) operators; for example, the Royal Logistic Corps contains a specialist unit of ammunition technicians, trained in disposing of chemical, biological, incendiary, radiological and nuclear weapons.They provide support to VIPs, help civilian authorities with bomb problems, teach personnel from all three services about bomb safety, and a variety of other tasks. All prospective ammunition technicians attend a gruelling course of instruction at The Army School of Ammunition and the Felix Centre, United Kingdom.

Nonetheless, a lot of the smaller items lying around the UK, such as mortars, grenades and small-arms ammunition, are actually found by the general public and metal detectorists. The larger items like aerial bombs tend to be buried at a much greater depth, and so it is construction workers who find the bulk of them. Fishermen can also drag up unexploded ordnance off the shores of the UK. The police and specialist military personnel are rarely the people who find unexploded ordnance; merely the ones who attend and deal with the ordnance once found.

Some might ask whether, in light of the recent discoveries (and the disruption they have caused) it's time for a dedicated campaign to clear Britain of these hugely dangerous devices lying beneath its surface.

But this would be a massive job and would take hundreds of years to complete. Just look at the WW1 battlefields, as even now, 100 years after the war ended, whole swathes of countryside are still full of unexploded munitions. The French government has designated certain areas around the WW1 battlefields as 'Red Zones', so highly contaminated with unexploded ordnance that many activities are totally prohibited.

In fact, in mainland Europe (and indeed in any country that the war passed through across the entire world) the problem is far greater than in the UK. As there were never any ground battles on UK soil, the amount of unexploded ordnance still lying undetected is tiny in comparison to France, Belgium and Germany. For example, during the whole of WW2, the RAF and USAAF dropped a combined total of over 1.5 million tons of bombs from their aircraft. The best guess at failure rates of Allied bombs is often quoted to be as high as 20%. That's 300,000 tons of unexploded bombs!

To give you an idea of the situation in Europe, here are two pictures of discoveries made on the continent. The first is a pile of German rifle grenades, S-mines, artillery shells and grenades. The second is a sample of around 300 7.62mm Russian cartridges, all live and all still potentially deadly.

Then if you factor in all the dropped or forgotten small arms ammunition, unexploded artillery shells, mortars, grenades, rockets....the ammo dumps underground still full and long since buried and forgotten...the list goes on and on. Even though the UK holds far less than other countries, there are still thousands of tons of high explosive munitions and small arms ammunition buried a couple of inches beneath the surface of our green and pleasant land.

Even if there was a dedicated campaign to clear the UK, the proponents would have two major issues: Firstly, that many of the official army ranges have long since been forgotten about so where do you search? Secondly, time and money would prohibit an active search in all but the most contaminated of areas. Even then, you can never be sure it will be totally clear of unexploded ordnance.

This means the unexploded ordnance lying under UK soil will never be fully cleared. Ever. No-one is actively looking for it for one thing. Secondly,you can never truly be sure an area is 100% clear. A saying often used by metal detectorist is that you have to walk over an item to find it. It made sound silly but is patently true, as an inch or two either side, and it goes undetected.

What's the upshot? Well, over the years, discoveries like the one made at London City Airport will continue to happen - a dream for journalists and news fans, but a nightmare for the people in the immediate vicinity, and those who have to deal with making the ordnance safe.

Stephen Taylor is well-known as a World War II relic hunter, having appeared extensively on the History Channel and written for military magazines.